Devices, such as a scanner and a printer, output device-dependent values (color values, like RGB values and CMYK values) which depend on the respective devices. To handle the device-dependent values, a color conversion table (a device profile) to convert device-dependent values into device-independent colors is created, and color conversion is performed on device-dependent values by using the device profile. As an example of a way to create a device profile, a description is now given of a way to create a scanner profile. To create a scanner profile, a color chart is output with a printer, and the color chart is measured with scanner and a color measurement device. RGB values obtained by the measurement of the color chart with the scanner and L*a*b* values in the CIE 1976 color space or XYZ values of the CIE 1931 color space obtained by the measurement of the color chart with the color measurement device are associated with each other, whereby a scanner profile can be created.
Since the above-mentioned scanner profile is created by measurement of a color chart printed with a printer, a change in the printer or printing conditions may affect an accuracy of color conversion using the scanner profile. That is, a change of the condition of the printer and/or a change of a paper type to be used in the printer may widen the color gamut of the printer (the range of colors that the printer can produce) in comparison with the color gamut of the printer at the time of creating the scanner profile. A use of the scanner profile under this situation can degrade of the accuracy of color conversion. In such a case, it is necessary to correct the scanner profile.